1. Log in to your Gmail account. Click the Gear icon at the top Right of the page.
2. Select “Settings” from the drop-down menu with gear icon. Click the “Accounts and Import” tab at the top. If you use Google Apps for domains, click the “Accounts” tab instead of “Accounts and Import”.
3. Scroll down to the Check Mail Using POP3 section in the sidebar, and click “Add POP3 email account you own.”
4. Enter the email address of the account you want Gmail to check in the Email Address box in the window that pops up. Click the “Next Step” button.
5. Enter your password for the account you want to check in the Password box. Verify that the POP server and Port fields have the correct information for your account.
6. Check the box next to the “Always use a secure connection (SSL) when retrieving mail” unless your email account provider explicitly told you not to. Read the other options regarding messages from that account and check the boxes next to the ones that you wish to enable.
7. Click on “Add Account” option.
Help take from: ehow.com